Subaru Legacy IV (2008 year). Manual - part 173

EN(H4SO)(diag)-295

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM.
3) Measure the resistance between ECM con-
nectors.

Connector & terminal

(B134) No. 19 — (B134) No. 18:
(B134) No. 19 — (B134) No. 28:

Is the resistance 1 M

: or 

more?

Repair poor con-
tact of the elec-
tronic throttle 
control connector. 
Replace the elec-
tronic throttle con-
trol if defective. 
<Ref. to 
FU(H4SO)-12, 
Throttle Body.>

Repair the short 
circuit to power in 
the harness 
between ECM and 
electronic throttle 
control connector.

Step

Check

Yes

No

EN(H4SO)(diag)-296

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DJ:DTC P2138 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D”/“E” VOLTAGE 

CORRELATION

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-196, DTC P2138 THROTTLE/PEDAL POSITION SEN-
SOR/SWITCH “D”/“E” VOLTAGE CORRELATION, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Improper idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06844

B315

E

C:

ECM

B136

B137

D:

B83

B315

*

*

4

6

5

1

3

2

D1

D2

1 2 3 4 5 6

B21

E2

D3

B122

1 2 3 4
5 6 7 8

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

B137

5

6

7

8

2

1

9

4

3

10

22 23

11 12 13 14 15

24 25

26

16 17

18 19 20 21

27

28 29

30 31

B136

5

6

7 8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26 27

28

16

17 18 19 20 21

33 34

29

32

30

31

35

B135

5

6

7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26 27

28

16 17 18 19

20 21

29 30 31

32 33

34 35

B:

B134

A:

C:

D:

B83

A5

B: B135

A: B134

D7

36

34

52

35

37

B122

ACCELERATOR 

PEDAL 

POSITION

SENSOR

E

*

*

 : TERMINAL No. OPTIONAL 
 ARRANGEMENT

*

B21

B23

B29

B22

B31

B30

C6

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22

28 29

9

17

18

25

21

23 24

32

31

26 27
33 34

EN(H4SO)(diag)-297

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK ACCELERATOR PEDAL POSITION 
SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM and 
chassis ground.

Connector & terminal

Main accelerator pedal position sensor 
signal

(B135) No. 23 (+) — Chassis ground (–):

Sub accelerator pedal position sensor 
signal

(B135) No. 31 (+) — Chassis ground (–):

Is the difference in measured 
values for the main accelerator 
pedal position sensor signal 
and the sub accelerator pedal 
position sensor signal 0 V?

Go to step 3.

Go to step 2.

2

CHECK ACCELERATOR PEDAL POSITION 
SENSOR OUTPUT.
1) Measure the voltage between accelerator 
pedal position sensor connector and chassis 
ground.

Connector & terminal

(B315) No. 6 (+) — Chassis ground (–):
(B315) No. 3 (+) — Chassis ground (–):

Is the difference in measured 
values for the main accelerator 
pedal position sensor signal 
and the sub accelerator pedal 
position sensor signal 0 V?

Replace the accel-
erator pedal. <Ref. 
to SP(H4SO)-3, 
Accelerator 
Pedal.>

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
the ECM and ac-
celerator pedal po-
sition sensor
connector.
• Short circuit to
ground in harness
between ECM and
accelerator pedal
position sensor
connector.
• Poor contact of
coupling connector

3

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR 
CONNECTOR.
Check the resistance of harness between the 
accelerator pedal position sensor connector 
and chassis ground.

Connector & terminal

(B315) No. 5 — Chassis ground:
(B315) No. 2 — Chassis ground:

Is the resistance less than 5 

:? Repair the poor 

contact of ECM 
connector.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
the ECM and ac-
celerator pedal po-
sition sensor
connector.
• Open circuit of
harness between
ECM and engine
ground
• Poor contact in
ECM connector
• Poor contact of
coupling connector

EN(H4SO)(diag)-298

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DK:DTC P2227 BAROMETRIC PRESSURE CIRCUIT RANGE/PERFORMANCE

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-198, DTC P2227 BAROMETRIC PRESSURE CIRCUIT
RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.

DL:DTC P2228 BAROMETRIC PRESSURE CIRCUIT LOW

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-199, DTC P2228 BAROMETRIC PRESSURE CIRCUIT
LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H4SO)(diag)-
80, List of Diagnos-
tic Trouble Code 
(DTC).>

Replace the ECM. 
<Ref. to 
FU(H4SO)-39,
Engine Control 
Module (ECM).>

NOTE:
The barometric
pressure sensor is
built into the ECM.

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H4SO)(diag)-
80, List of Diagnos-
tic Trouble Code 
(DTC).>

Replace the ECM. 
<Ref. to 
FU(H4SO)-39,
Engine Control 
Module (ECM).>

NOTE:
The barometric
pressure sensor is
built into the ECM.